1. Field of the Invention
The present invention relates to power management within a computer system.
2. Description of the Related Art
Energy savings has become a key issue in many fields, including the computer industry. Most computer users and computer manufacturers have made efforts to increase power efficiency within computer systems to provide for a net energy savings that is beneficial both to the consumer, as a means of saving money on energy costs, and to the environment, by reducing overall energy consumption.
One common source of power inefficiency in computers is the energy used in maintaining rotation of disks within a hard disk drive while the computer is powered on and no accesses are being made to the disk drive. In certain applications, computer manufacturers have found it advantageous to manage the operation of the hard disk so as to obtain significant power savings.
For example, some desktop computers now include disk power management which causes a hard drive within the desktop computer to spin down when the computer has been inactive for some predetermined period of time. Certain desktop and laptop computer systems spin down the disk drive based upon previous monitoring of the user's habits. Thus, for instance, if previous monitoring of the user's habits indicates that when the user is away for more than five minutes the user typically does not return for a long time period, then the desktop or laptop computer will spin down the hard drive when a period of inactivity greater than five minutes is detected.
Although disk power management in desktop and notebook computer environments has been found to be straightforward in implementation, disk power management in network servers has met with several obstacles in the past. First, the entire network operating system is typically shut down whenever the network server is down. This makes the server unavailable to users who work late at night, or, if a company has an international business, employees in other countries would not have access to the network server in what would be daytime working hours to these international employees. Furthermore, with the network server powered down, tape backups of the network disk drives would be impossible.
A further reason for not powering down a server on a daily basis is that powering down the server would put undue thermal stress on the electronic components within the network server by heating and cooling them. This can cause the electronic components to fracture or come out of their sockets, causing a failure. This heating and cooling may also cause undue stress to circuit boards which have surface mount components. For these reasons, powering the entire server up and down on any regular basis would be impractical.
Furthermore, network servers, unlike notebook or desktop computers, include a network operating system which does not communicate with the disk drive controller through a standard interface BIOS (basic input/output system). Thus, what would be a straightforward implementation of a power management scheme to control the operation of spinning up and spinning down the disk drives in a notebook or desktop environment, is not straightforward for network servers. This is, in part, because notebook or desktop computers are able to control the spinning up and spinning down of disk drives within the notebook or desktop computers via standard commands issued to the BIOS. But since the operating systems of network shvers require a device driver application layer which is often custom designed for a given network operating system, a network server cannot simply spin up or spin down the disk drives within the network server using conventional commands without regard to the device driver used in accordance with the network operating system.
Finally, a typical mindset that servers are better left running continuously is still prevalent because disk drives in past servers were likely to not spin back up after being spun down. Thus, this mindset contributes to the reasons why disk drives in network servers are not spun down for purposes of power management.